Project Description

BedSense – Contactless bedsensor

New technology for measuring sleep or sleep disorders

Within the BedSense project a newly developed, extremely sensitive pressure sensor is placed under the mattress to monitor even the smallest change in pressure. This contactless bedsensor is used to detect presence, movements, breathing rate and heart rate reliably. Benefit of placing the sensor under the mattress is that the existing mattress can be used and that users, also after months of use, do not feel the sensor at all.Raw information is stored in high-resolution on SD-card. At the moment the functional prototype is validated at Kempenhaeghe, the leading sleep centre in the Netherlands for sleep disorders and epilepsy. BedSense measurements are compared to the golden standard: the Kempenhaeghe polysomnography system.These measurements will help to refine the various signal processing algorithms for automatic feature extraction for specific diseases and patient groups.Current focus is on three use cases: effectiveness of sleep interventions in the home environment (like OSA), sleep quality for Parkinson patients and epilepsy detection.

Key features

Accurate & medically validated sleep monitoring.

Contactless, placed under the mattress

Presence, movements, breathing, heart rate

Medical research, clinical and home applications

This project was made possible by a contribution from the European Regional Development Fund as part of OP-Zuid. For more information see EFRO.

BedSense system

The BedSense system exists of the following components:

BedSense datalogger, functions:

Store measurements of upto 3 sensors in raw format for later signal analysis

Live data-feed in Matlab for real-time testing of features (via USB interface)

1-3 BedSense contactless bedsensor’s

Accessories:

Power supply (5V)

Micro SD card + adapter card

External sync: TTL, 3.5mm jack cable

Remote control: start/stop recordings and check recording status when the BedSense system is placed under a hospital bed.

Technical specifications

Sensing

Sensors: 1 to 3 sensors

Sampling Rate: 100 Hz

Sampling Rate Drift: 0.021% / ºC

ADC Resolution: 24 bit (20bit effective)

External synchronization

Sync Pulse: K x 0.5 seconds with K=1-144

Sync Amplitude: 0 volt (off) – 3 volt (on)

Sync Frequency: 10 minutes (first pulse; K=1 at t=0 sec)

Sync Interface: 3.5mm mono jack plug

Power: 5V power adapter and internal battery powered (upto 10 hours)

Recordings: max 100 files

Storage: 32Gb micro SD card

Data output

Stored data files can be exported to BDF format with the supplied BDF convertor. BDF is the 24-bits version of the EDF file. BDF files can be viewed with multiple (open source) software packages like EDFBrowser. The BDF file contains 3 data signals per each connected sensor channel XX:

ChXX: 24 bit sensor data

ChXX_Syncpulse: Sensor synchronization pulses

ChXX_Temperature: Sensor temperature (updated every 0.5sec)

So when all 3 sensors were connected, the BDF file holds 9 signals in total.

Current status

122 complete night recordings have been made at Kempenhaeghe which are currently analyzed and used for creation of new algorithms. BedSense is available as a research evaluation prototype for detailed monitoring of people and patients. Besides additional technical and medical research we are investigating the possibilities for embedding the technology into existing and new applications. Date: 06-03-2018